I. Field of the Invention.
This invention relates generally to an improved apparatus for cutting concrete materials and the like and more particularly, to a circular concrete cutting saw in which a fluid, such as water, is used to cool both sides of the saw blade.
II. Brief Description of the Prior Art.
Fluid-cooled circular saws used for cutting materials such as wood, or even concrete, have been in existence for a number of years. An excellent description of the various types of devices that have been developed can be found in Hogue, U.S. Pat. No. 4,570,609, issued Feb. 18, 1986.
In general, the basic device consists of a large disc-shaped cutting blade which is attached to a hub on one side of the blade and then affixed to a rotatable shaft powered by a motor. When the shaft is rotated, the blade spins in a circular fashion and teeth on the blade gouge into the surface to be cut, thereby forming a cut line in the surface of the concrete. When materials such as concrete are cut, diamond-impregnated steel is used on the cutting tips, or teeth, of the saw to assure that the blades do not wear as easily as less hardened materials, and to provide a cleaner cut.
The diamond-impregnated cutting teeth of the blade are usually attached to the circular saw plate by either soldering or an adhesive material. When the blades are rotating at high speeds and are cutting into hardened materials, the blade and attached hub will get hot enough to break down the adhesive or solder joint. In addition, if the blade or hub is allowed to get too hot, stress fractures in the metal will occur. Regardless of whether only the teeth become detached from the blade, or the blade or hub is also fractured, hardened pieces of metal can be driven away from the saw at speeds approaching that of a bullet. Rough metal traveling at such great speeds can easily pierce protective guard housing surrounding the blade and cause injury to the operator as well as cause great damage to the equipment. In addition, excessive heat prematurely ages the life of the blade. Thus, unless both the hub and both sides of the saw blade (including the teeth) are sufficiently cooled, various parts will have to be continuously replaced, which results in high operating costs.
Prior art devices such as Hogue or Manning, U.S. Pat. No. 3,896,783, issued July 29, 1975, have attempted to water-cool the blade and hub in a variety of ways. In Manning, a tube is attached to an inlet device affixed to the top of the blade guard, which has a number of thinner tubes that run along its inside walls. When water is introduced into the system, small openings in the thin internal tubes of the guard cause fluid to spray on the sides of the blade. However, when cooling fluid is sprayed on the blades, only exposed portions of the blade can be cooled, thus, the area between where the hub and blade contact and the cutting area may not be sufficiently cooled. In Hogue, tubes mounted on the guard also spray fluid onto the outer surface of the blade, as well as spray fluid into a doughnut-shaped annular groove in the hub, from which the spinning motion of the hub centrifugally disperses the fluid through small passageways running perpendicular to the surface of the blade (or parallel to the shaft) and through the hub to the external side of the blade. The inadequacies of this method of fluid-cooling will be discussed below.
Aside from the prior art's limited ability to disperse cooling fluid to needed areas of the saw, neither Hogue nor Manning adequately take into consideration the working environment in which such saws are used. In use, the saws tend to be handled roughly, such as dropped or thrown in the back of trucks, which often results in damage to the blade guard. In addition, if a particular cut is not made correctly, the blade of the saw can be pushed into the guard protecting the blade, which results in damage to the guard and cooling tubes, as well as the blade.
Hogue teaches that for flush cut applications fluid can be introduced into the hub area and then delivered by centrifugal force to the distal end of the hub for dispersal to the outer surface of the blade. However, the method taught by Hogue is far from effective. As fluid is sprayed into the rearwardly opening, doughnut-shaped annular groove in the hub, centrifugal force is relied on to push the fluid collecting in the groove through openings in the hub to the external side of the blade. While some fluid inevitably travels to the external surface of the blade, some fluid will also escape through the rearward opening of the groove and therefore have absolutely no effect in cooling the blade. In addition, because the fluid in the groove is not under positive pressurized flow, only centrifugal forces will cause the fluid to flow down this passageway in the hub. In Hogue, the passageways between the rear groove and the outlets on the opposite side of the blade appear to be parallel to the shaft. Centrifugal force on fluid in this passageway would be perpendicular to the rotational direction of the shaft, not parallel, thus the fluid is not actually forced to flow down the shaft and may even stop flowing along the passageways in some situations.
Due to the limited cooling feature of prior art flush cutting saws, one person has been required to operate the saw while a second person either squeegeed or hosed water into the cutting area so that the saw could be sufficiently cooled. In addition, the extra tubing and enlarged guard required by the prior art saws adds a significant amount of weight to the saw, further restricting its operation as well as its portability.
When prior art saws are used for flush cutting (such as cutting a groove in the floor along a wall), one side of the blade wears substantially faster than the opposite side of the blade. While the exaggerated wear is, in part, due to insufficient cooling, it is accented by the fact that the construction of the hubs, blades and cooling tubes are such that the blades can not be reversed so as to extend the life-span of the blades. Because a truly reversible saw blade would require twice the number of holes as a one-sided blade, and would be further weakened and prone to stress-fracturing than a one-sided blade, it is important that the cooling system of a reversible blade saw be better than that of nonreversible saws. Thus if the saw has an improved, highly efficient cooling system in accordance with the present invention, the additional holes necessary for a reversible blade can be added without reducing the strength of the blade or increasing the likelihood of stress fracturing.
An additional limitation of prior art saws is that a different hub is required when the saw is used for flush-cut operation than when the saw is used for open-cut operation. The removal and replacement of one hub with different hubs results in increased labor, additional tooling and other extra costs.